Built on low-lying ground that floods when the river rises, this substantial fortification represents centuries of medieval military architecture. The castle’s location wasn’t chosen by accident; controlling the Barrow meant controlling one of Ireland’s major transport routes during the medieval period.

What remains today hints at the castle’s former grandeur. The central keep, though now largely ruined, was originally an oblong structure defended by four massive round towers at each corner, with only the northern tower still standing. The entire complex was surrounded by extensive fortified walls, or bawn, which created a formidable defensive perimeter. A broad water-filled trench, roughly 10 metres wide, once encircled the entire fortress, adding another layer of protection against would-be attackers. The gateway itself was no simple entrance but rather a miniature castle complete with a portcullis, designed to be defended independently if the outer walls were breached.

The site may be even older than the stone castle suggests. The water-filled fosse could be the remnant of an earlier ringwork, a type of earthwork fortification typically used for wooden castles in the early Norman period. This would mean the site evolved from a timber fortress into the stone stronghold whose ruins we see today, following a pattern seen at other Norman sites across Ireland. The castle’s design bears striking similarities to other major Anglo-Norman fortifications, particularly the Le Marshall Castle at Carlow, suggesting it was built by the same military architects or at least following the same defensive principles that proved successful elsewhere in medieval Ireland.